The present invention relates to an agricultural pulling machine, especially a tractor for a construction machine vehicle with a working attachment coupled through a mounting device and with a device for active damping of pitch vibrations of the vehicle.
Pulling machines of the above mentioned general type are known in the art. The German reference DE-OS 3,446,811 discloses a vehicle in which a plow is articulatedly connected with a tractor through a three-point linkage, and an active vibration damping of the attachment in its lifted position is performed through the electrohydraulic regulating device for plow adjustment. With such a system for dynamic stabilization of the movements of the vehicle, the pitch vibrations can be reduced so that with the attachment lifted, high transporting speeds and a high tearing safety are possible. For such a vibration damping, preferably the force regulating circuit and its associated force sensor are used. In this construction unfavorable operational conditions can occur, so that due to inaccurate signal detection, influences are produced which affect the quality of the vibration damping and can lead to increased movement amplitude of the attachment. The horizontal forces determined in levers by a force sensor can change during travel on curves, and/or during lateral swinging of the attachment when a part of the side guiding linkage connected with the lever transmits the horizontal forces to the housing of the tractor and thereby the accuracy of the results of the measurement is affected. The same is true also for tractor types in which the side guiding linkage includes not rigid rods, but instead pulling chains. Also in many types of tractors it is conventional to provide for this side guidance with additional supporting surfaces or cams attached to the housing, which limit lateral breakage of the levers.
The German reference DE-OS No. 3,346,892 discloses a vehicle with an articulately connected attachment. Here, the pitch vibrations of the tractor must be damped with the electrohydraulic lifting mechanism regulating device. A damping must here be achieved because the attachment in the vertical position is held spatially in an approximately immovable manner. For influencing and controlling transverse vibrations of the plow attached to the tractor, in this vehicle no measures are provided.
The patent document EP-No. A1-0 033,923 discloses a tractor with an electrohydraulic regulating device for plow adjustment. Here the lower lever is supported through force measuring pins on the housing of the tractor. The regulating device is operated with the sum of both signals of force measuring pins. An active vibration damping is here not provided. Unfavorable conditions for the force detection can take place especially when the connecting point of both levers on the housing of the tractor lie near one another and the lower lever which curves downwardly in a V-shaped manner, is supported through inclined side guiding linkage on the tractor frame, so that for example during travel on curves a part of the horizontal forces is transmitted to the housing of the tractor.